1. Field of the Invention
The present invention relates to a display device, and more particularly to a technology that can be effectively applied to a TFT liquid crystal display device.
2. Description of the Related Art
A TFT liquid crystal display device has been used as a display device for TVs, personal computer monitors, and the like.
The TFT liquid crystal display device has a liquid crystal display panel that is obtained by interposing liquid crystal between two substrates. One of the two substrates is generally referred to as a TFT substrate. The TFT substrate is obtained, for instance, by forming plural scanning signal lines, plural video signal lines, plural TFTs, and plural pixel electrodes on the surface of a glass substrate or other insulated substrate. The other substrate is generally referred to as a counter substrate. The counter substrate is obtained, for instance, by forming a lighttight film for dividing a display area into individual pixel regions and a color filter on the surface of a glass substrate or other insulated substrate. Counter electrodes, which drive the liquid crystal in conjunction with the pixel electrodes, are formed on either the TFT substrate or the counter substrate.
The liquid crystal display panel has a display area for displaying motion pictures and still pictures. The display area is composed of a large number of pixels. Each pixel has a TFT and a pixel electrode that is connected to the source of the TFT. In this instance, the drain of each TFT is connected to a video signal line, whereas the gate of each TFT is connected to a scanning signal line. As regards the source and drain of each TFT, this document assumes that the source is connected to a pixel electrode while the drain is connected to a video signal line. In some cases, however, the reverse may apply. More specifically, it may be assumed that the drain is connected to a pixel electrode while the source is connected to a video signal line.
In the above-mentioned conventional liquid crystal display panel, plural pixel electrodes that are positioned between two neighboring video signal lines and arranged in the extending direction of the video signal lines are connected, for instance, to one of the two neighboring video signal lines through a TFT connected to each pixel electrode. In this case, a common conventional liquid crystal display panel is configured so that all the drains of TFTs connected to the pixel electrodes are connected to the same video signal line of the two neighboring video signal lines.
In a recently developed liquid crystal display panel, which is disclosed, for instance, by Japanese Patent JP-A No. 1998-90712, a TFT whose drain is connected to one of two neighboring video signal lines and a TFT whose drain is connected to the other video signal line are positioned between the two neighboring video signal lines and alternately arranged in the extending direction of the video signal lines. In the above liquid crystal display panel, plural pixel electrodes, which are positioned between two neighboring video signal lines and arranged in the extending direction of the video signal lines, are configured so that, for example, a pixel electrode connected to one of the two neighboring video signal lines through a TFT and a pixel electrode connected to the other video signal line are alternately arranged in the extending direction of the video signal lines.
In recent years, liquid crystal TVs and other liquid crystal display devices have increased their refresh rates in order to minimize screen flicker and improve motion picture display performance.
However, when the refresh rates of conventional liquid crystal display devices were increased, tone voltages written into the pixel electrodes through the TFTs were insufficient. This resulted in image quality deterioration.
Further, when the conventional liquid crystal display devices were used, plural pixel electrodes whose drains were connected to the same video signal line differed in written tone voltage insufficiency. Thus, a phenomenon called “lateral stripes” occurred to the detriment of image quality.